Hall Effect transistors and magnets are frequently used as components in tamper alarm circuits to detect relative motion, i.e. the opening of a door, window, container, fastener, etc. with respect to a stationary component. Disadvantages of Hall Effect transistors as used in prior art alarm systems and devices are: possible misalignment of transistor and magnet, sensitivity to spurious motion, lower sensitivity, and ease in defeating the systems. The mere use of an external magnet can "spoof" such devices and cause them not to respond when opened. The need to make the alarm systems more tamper resistant is obvious.